///////////////////////////////////////////////////////////////////////////////
//
/// \file       sha256.c
/// \brief      SHA256
//
//  Based on the public domain code found from Wei Dai's Crypto++ library
//  version 5.5.1: http://www.cryptopp.com/
//  This code has been put into the public domain.
//
/// \todo       Crypto++ has x86 ASM optimizations. They use SSE so if they
///             are imported to liblzma, SSE instructions need to be used
///             conditionally to keep the code working on older boxes.
//
//  This library is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
//
///////////////////////////////////////////////////////////////////////////////

#include "check.h"

#ifndef WORDS_BIGENDIAN
#	include "check_byteswap.h"
#endif

// At least on x86, GCC is able to optimize this to a rotate instruction.
#define rotr_32(num, amount) ((num) >> (amount) | (num) << (32 - (amount)))

#define blk0(i) (W[i] = data[i])
#define blk2(i) (W[i & 15] += s1(W[(i - 2) & 15]) + W[(i - 7) & 15] \
		+ s0(W[(i - 15) & 15]))

#define Ch(x, y, z) (z ^ (x & (y ^ z)))
#define Maj(x, y, z) ((x & y) | (z & (x | y)))

#define a(i) T[(0 - i) & 7]
#define b(i) T[(1 - i) & 7]
#define c(i) T[(2 - i) & 7]
#define d(i) T[(3 - i) & 7]
#define e(i) T[(4 - i) & 7]
#define f(i) T[(5 - i) & 7]
#define g(i) T[(6 - i) & 7]
#define h(i) T[(7 - i) & 7]

#define R(i) \
	h(i) += S1(e(i)) + Ch(e(i), f(i), g(i)) + SHA256_K[i + j] \
		+ (j ? blk2(i) : blk0(i)); \
	d(i) += h(i); \
	h(i) += S0(a(i)) + Maj(a(i), b(i), c(i))

#define S0(x) (rotr_32(x, 2) ^ rotr_32(x, 13) ^ rotr_32(x, 22))
#define S1(x) (rotr_32(x, 6) ^ rotr_32(x, 11) ^ rotr_32(x, 25))
#define s0(x) (rotr_32(x, 7) ^ rotr_32(x, 18) ^ (x >> 3))
#define s1(x) (rotr_32(x, 17) ^ rotr_32(x, 19) ^ (x >> 10))


static const uint32_t SHA256_K[64] = {
	0x428A2F98, 0x71374491, 0xB5C0FBCF, 0xE9B5DBA5,
	0x3956C25B, 0x59F111F1, 0x923F82A4, 0xAB1C5ED5,
	0xD807AA98, 0x12835B01, 0x243185BE, 0x550C7DC3,
	0x72BE5D74, 0x80DEB1FE, 0x9BDC06A7, 0xC19BF174,
	0xE49B69C1, 0xEFBE4786, 0x0FC19DC6, 0x240CA1CC,
	0x2DE92C6F, 0x4A7484AA, 0x5CB0A9DC, 0x76F988DA,
	0x983E5152, 0xA831C66D, 0xB00327C8, 0xBF597FC7,
	0xC6E00BF3, 0xD5A79147, 0x06CA6351, 0x14292967,
	0x27B70A85, 0x2E1B2138, 0x4D2C6DFC, 0x53380D13,
	0x650A7354, 0x766A0ABB, 0x81C2C92E, 0x92722C85,
	0xA2BFE8A1, 0xA81A664B, 0xC24B8B70, 0xC76C51A3,
	0xD192E819, 0xD6990624, 0xF40E3585, 0x106AA070,
	0x19A4C116, 0x1E376C08, 0x2748774C, 0x34B0BCB5,
	0x391C0CB3, 0x4ED8AA4A, 0x5B9CCA4F, 0x682E6FF3,
	0x748F82EE, 0x78A5636F, 0x84C87814, 0x8CC70208,
	0x90BEFFFA, 0xA4506CEB, 0xBEF9A3F7, 0xC67178F2,
};


static void
transform(uint32_t state[static 8], const uint32_t data[static 16])
{
	uint32_t W[16];
	uint32_t T[8];

	// Copy state[] to working vars.
	memcpy(T, state, sizeof(T));

	// 64 operations, partially loop unrolled
	for (unsigned int j = 0; j < 64; j += 16) {
		R( 0); R( 1); R( 2); R( 3);
		R( 4); R( 5); R( 6); R( 7);
		R( 8); R( 9); R(10); R(11);
		R(12); R(13); R(14); R(15);
	}

	// Add the working vars back into state[].
	state[0] += a(0);
	state[1] += b(0);
	state[2] += c(0);
	state[3] += d(0);
	state[4] += e(0);
	state[5] += f(0);
	state[6] += g(0);
	state[7] += h(0);
}


static void
process(lzma_sha256 *sha256)
{
#ifdef WORDS_BIGENDIAN
	transform(sha256->state, (uint32_t *)(sha256->buffer));

#else
	uint32_t data[16];

	for (size_t i = 0; i < 16; ++i)
		data[i] = bswap_32(*((uint32_t*)(sha256->buffer) + i));

	transform(sha256->state, data);
#endif

	return;
}


extern void
lzma_sha256_init(lzma_sha256 *sha256)
{
	static const uint32_t s[8] = {
		0x6A09E667, 0xBB67AE85, 0x3C6EF372, 0xA54FF53A,
		0x510E527F, 0x9B05688C, 0x1F83D9AB, 0x5BE0CD19,
	};

	memcpy(sha256->state, s, sizeof(s));
	sha256->size = 0;

	return;
}


extern void
lzma_sha256_update(const uint8_t *buf, size_t size, lzma_sha256 *sha256)
{
	// Copy the input data into a properly aligned temporary buffer.
	// This way we can be called with arbitrarily sized buffers
	// (no need to be multiple of 64 bytes), and the code works also
	// on architectures that don't allow unaligned memory access.
	while (size > 0) {
		const size_t copy_start = sha256->size & 0x3F;
		size_t copy_size = 64 - copy_start;
		if (copy_size > size)
			copy_size = size;

		memcpy(sha256->buffer + copy_start, buf, copy_size);

		buf += copy_size;
		size -= copy_size;
		sha256->size += copy_size;

		if ((sha256->size & 0x3F) == 0)
			process(sha256);
	}

	return;
}


extern void
lzma_sha256_finish(lzma_sha256 *sha256)
{
	// Add padding as described in RFC 3174 (it describes SHA-1 but
	// the same padding style is used for SHA-256 too).
	size_t pos = sha256->size & 0x3F;
	sha256->buffer[pos++] = 0x80;

	while (pos != 64 - 8) {
		if (pos == 64) {
			process(sha256);
			pos = 0;
		}

		sha256->buffer[pos++] = 0x00;
	}

	// Convert the message size from bytes to bits.
	sha256->size *= 8;

#ifdef WORDS_BIGENDIAN
	*(uint64_t *)(sha256->buffer + 64 - 8) = sha256->size;
#else
	*(uint64_t *)(sha256->buffer + 64 - 8) = bswap_64(sha256->size);
#endif

	process(sha256);

	for (size_t i = 0; i < 8; ++i)
#ifdef WORDS_BIGENDIAN
		((uint32_t *)(sha256->buffer))[i] = sha256->state[i];
#else
		((uint32_t *)(sha256->buffer))[i] = bswap_32(sha256->state[i]);
#endif

	return;
}